1. Field of the Invention
The present invention relates to a process for forming a plated film having a plated film portion having an aspect ratio of as high as 1 or greater, and a process for fabricating a magnetic device, and a perpendicular magnetic recording head using that process.
2. Explanation of the Prior Art
In the field of fabrication of various devices, frame plating techniques have so far been widely used for micropattern formation. According to one typical frame plating, a seed film is formed as an electrode film on one surface of a substrate, and a frame (a pattern film having an opening) is then formed on the seed film, after which a plated film is grown on a portion of the seed film exposed at the bottom of the opening to form a plated film pattern.
In the field of fabrication of various magnetic devices, there is often the need of forming a micro-pattern comprising a plated portion (high aspect-ratio portion) having an aspect ratio ((thickness/width) ratio) of greater than 1. Taking a perpendicular magnetic recording head as an example of the magnetic device, it is a magnetic pole layer that is corresponding to this type of micropattern, said magnetic pole layer having a function of guiding a magnetic flux to a magnetic recording medium, and having a microfine width portion for defining the recording track width of that magnetic recording medium.
For the efficient formation of a micropattern having a high aspect ratio within a short period of time, there is an improved frame plating technique now available, with which not only is a film formed by plating from the bottom of an opening but a film is also formed by plating along the inner wall surface from the opening. This improved frame plating technique typically involves the following steps: a resist pattern having an opening (in the form of, for instance, a concave groove) is formed, then an inorganic film is formed at the bottom and inner wall surface of the opening in the resist pattern, then a seed film is formed as an electrode film on the inorganic film, and finally a plated film is grown from the bottom and inner wall surface of the opening with the seed film formed over it.
However, when a photoresist coated on the surface of a substrate is exposed to monochromatic light for the purpose of forming a resist pattern having an opening (in the form of, for instance, a concave groove), there is a portion where light entering the resist and light reflected off the surface of the substrate are well periodically amplified according to wavelengths. This in turn causes a standing wave to be created at the inner wall surface of the resist at a site with the opening formed according to an amplified period. As, in the presence of this standing wave, the seed film working as the electrode film is formed on that via the inorganic film, it causes the standing wave to remain on the inner wall surface of the seed film in a wave form traced from that standing wave as it stands. As, in this state, the opening is buried up by a plated film that grows from the bottom and inner wall surface of the opening that provides a base for a high aspect-ratio plated film portion, there are pores (cavities) likely to occur within the plated film under increased influences of plating growth from the inner wall surface at which the standing wave is present. When the plated film having such pores (cavities) is used as the main magnetic pole of a perpendicular magnetic head as an example, there is a disruption in the magnetic domain structure of the main magnetic pole, or a plating solution remaining in the pores (cavities), which may otherwise end up with corrosion. As a result, the performance of the perpendicular-magnetic head becomes severely worse, or it does no longer function.
One possible approach to prevention of creation of standing waves is to form an antireflection film on the substrate (under the resist). However, for instance, it is very difficult to use an organic antireflection film with the process of forming the magnetic pole of a perpendicular magnetic head because of its process considerations. On the other hand, the use of an inorganic antireflection film comprising a nitride, because of having a very high hardness, may often cause much troubles at a head processing step. In other words, it is a presupposition to form the magnetic pole without using any antireflection film.
The invention of this application has been made with such situations in mind, and has for the object the provision of a process of fabricating a plated film, which enables a plated film portion having an aspect ratio of as high as 1 or greater to be efficiently formed in a short period of time and ensures that the formed plated film quality is very excellent for the reason of being free from pores (cavities), and a process of fabricating a magnetic device, and a perpendicular magnetic recording head using that process.